1. Field of the Invention
The invention relates in general to an analog to digital converter, and more particularly to an analog to digital converter capable of finding an analog value corresponding to a partial range of a digital value by executing interpolation.
2. Description of the Related Art
With the rapid advance in technology, liquid crystal display has been widely used in various electronic display products such as TVs, computer monitors, notebook computers, mobile phones and personal digital assistants. A data driver of the liquid crystal display includes an analog to digital converter providing a pixel voltage to the liquid crystal display panel according to the values of a grey level. A scan driver of the liquid crystal display is used for scanning the pixel voltage to each pixel of the liquid crystal display panel so as to display an image.
Since the relationship between a pixel voltage and its corresponding values of a grey level is non-linear, the conventional analog to digital converter converts the grey level into the pixel voltage through a Gamma voltage resistor string and subsequently inputs the pixel voltage to the liquid crystal display panel. However, as the display quality required of the liquid crystal display is getting higher and higher, the bit number of the grey level and the grade of the Gamma voltage resistor string increase dramatically. As the analog to digital converter requires a large circuit area, the cost is increased accordingly. The conventional design of down-sizing the analog to digital converter by using interpolation for each digital code has the shortcomings that the pixel voltage has larger error, and the liquid crystal display has poorer display quality.